1. Field of the Invention
The present invention relates to a recording apparatus and a method of detecting a malfunction of an ink detection means, and more particularly to an ink jet recording apparatus in a facsimile apparatus, a printer or a copying machine having means for detecting a residual quantity of ink mounted thereon and a method of detecting a malfunction of the means for detecting the residual quantity of ink.
2. Related Background Art
Hitherto, a variety of recording apparatuses arranged to record information on a recording medium, such as paper or an OHP sheet, have been suggested. An ink jet recording apparatus directly jetting ink from a recording head to the recording sheet has been used as a recording apparatus having a low running cost and silent recording operation.
As a method of detecting a residual quantity of ink for a conventional ink jet recording apparatus, a method has been employed in which a mark for detecting whether or not ink exists is recorded on a recording medium so as to be detected by a reflection-type photosensor. If the mark is not detected by the photosensor, a determination is performed that the ink has been consumed. As an alternative to this, ink is discharged to a position between a light emitting device and a light receiving device of a photointerrupter so as to detect existence of ink in accordance with a change in the output when the ink traverses the optical axis. If no ink is detected, a determination is performed that the ink has been consumed.
Although in the foregoing method for detecting whether or not ink exists it is required to record a mark on the recording medium which is not required for the recording operation, a satisfactory detection accuracy can be realized. However, foreign matter in the air can adhere to the reflecting type photosensor, causing an error in ink detection.
In the method of detecting whether ink exists in accordance with the change in the output when ink traverses the optical axis, it is required for the ink to optically shield the optical axis. To achieve this, a slit formed between the light emitting device and the light receiving device must have a small width because the ink droplet is very small. However, a slit having such a small width can sometimes be filled with fine mists of ink generated in a large quantity when ink is discharged or ink which comes in contact with the recording medium may afterward adhere to the slit. In the foregoing cases, detection cannot be performed. Moreover, so-called house dust is sometimes allowed to adhere to the slit and deposit on the slit portion, thus causing an error to take place in detection.
In a case where ink of a type having high viscosity is used, ink allowed to pass through the optical axis of the photointerrupter and received by the ink receiver is deposited and overlapped, thus resulting in a deposit like a stalactite being formed. If the deposit is enlarged so that its height from the receiving surface of the ink receiver reaches the optical axis, the optical axis of the photointerrupter can be shielded. If the foregoing state is realized, the optical axis is always shielded and, therefore, existence of ink cannot be detected.